Vampires have been roaming the world for millions of years, but they've managed to stay in hiding almost the entirety of their existence. Although, it wasn't unusual for one to reveal themselves to a human, usually with the intent to kill said human. There were the rare cases, however, when a vampire would fall in love with a human. These never ended well. When Kyungsoo falls in love with a human, it's up to him whether or not to change the immortal into one of his own, or never see him again.